1. Field of the Invention
The present invention relates to a method and a device for manufacturing an assembly of two ringed sheaths that can be detached from one another to make a single ringed sheath around a bundle of electric cables for example.
More specifically, in the method of the invention, two smooth-walled tubes are simultaneously extruded using an extruder fitted with two extrusion nozzles and the two smooth-walled tubes are simultaneously moulded into two ringed-wall tubes using a moulder equipped with moulds each fitted with two ringed profiles extending in parallel in a longitudinal direction and being paired along the same mating plane.
2. Description of the Related Art
It will be remembered that the bundle of electric cables which is provided in a car conventionally constitutes electric wires with a round cross-section, assembled in wire strands. Once these strands have been formed, the bundle is provided with various protective elements, before being fixed onto different elements of the vehicle, such as the engine and the car body.
Ringed tubular sheaths are one of the types of protection for bundles of electric cables commonly used in the car industry. The ringed tubular sheaths, formed by moulding an extruded tube into a succession of rings, are usually produced from extruded plastics materials, such as polypropylene, polyamide or polyesters. These sheaths provide a high resistance to abrasion and crushing, while maintaining a high level of flexibility which facilitates the production and packaging of the protected cabling, and the installation thereof in the vehicle. However, it is difficult to thread the strand within the ringed sheath, in particular in long portions. This is why split ringed sheaths are often used, i.e. ones which are cut along a straight longitudinal line at the end of the production process. It is thus possible subsequently to introduce electric wires and cables directly into any region of the sheath through the split.
The split ringed sheaths may include more or less complex closing systems so as to prevent the tube from allowing wires to escape in regions where the split tends to reopen. Document DE 196 41 421 in particular discloses a sheath of this type. These closing systems have been found to be relatively ineffective in regions with low radii of curvature.
Equally, the split ringed sheaths may be completely strapped up once they have been positioned on the bundle of cables, and this effectively locks the split, but requires an additional operation from the person laying the cables.
Another solution involves using an assembly of two sheaths as described in document EP 0 268 869: in this technique, the assembly consists of a first split ringed sheath positioned on the bundle of electric cables which is to be protected, and a second split ringed sheath of a greater diameter in which the first ringed sheath is housed. However, the use of an assembly of two separate elements complicates the arrangement, the cut along the protective covering, and the mounting operations for the person laying the cables.